The present invention relates generally to an integrally molded brush having a plurality of bristles extending from a generally planar hub and to a method of molding an integrally molded brush. The present invention relates more particularly to an integrally molded brush comprising thermoplastic polymeric material having a generally planar hub with a thickness of at least 0.050 inches (0.13 cm.) and a plurality of bristles with bristle tip thickness of up to 0.030 inches (0.076 cm.).
Brushes have been used for many years to polish, clean, and abrade a wide variety of substrates. These brush products typically have a plurality of bristles that contact the substrate. Abrasive particles can be added to bristles to increase their aggressiveness. There are many manufacturing steps necessary to manufacture a conventional abrasive brush having bristles that contain abrasive particles. A mixture of abrasive particles and a thermoplastic binder may be combined and then extruded to form a bristle. The bristle is then cut to the desired length. A plurality of these bristles are then mechanically combined to form a brush segment. Next, a plurality of these brush segments may be installed on a hub or plate to form a brush.
Another example of a brush is disclosed in U.S. Pat. No. 5,903,951, xe2x80x9cMolded Brush Segment,xe2x80x9d (Ionta et al.). In Ionta et al., a brush segment is integrally molded having a plurality of bristles extending from a generally planar center portion. The brush segment is molded from a moldable polymer such as a thermoset polymer, thermoplastic polymer, or thermoplastic elastomer. The moldable polymer preferably includes a plurality of organic or inorganic abrasive particles interspersed throughout at least the bristles, and can be interspersed throughout the brush segment. The molded brush segments can be generally circular, with the bristles extending radially outward in the plane defined by the central portion. A plurality of brush segments can be combined to form a brush assembly. Ionta et al. also discloses a method of making a molded abrasive brush and a method of refining a workpiece surface with a molded abrasive brush.
Although the commercial success of available integrally molded brushes comprising thermoplastic polymeric material has been impressive, it is desirable to further minimize the thickness of the bristle tips. Such bristles can be used, for example, to abrade small grooves, such as threads on bolts. However, it has been very difficult to integrally mold a brush with such thin bristle tips because of the tendency of the molten thermoplastic polymeric material to solidify in the mold cavity before substantially filling the bristle portions of the mold.
The present invention provides an integrally molded brush and method for making the same. One aspect of the present invention provides an integrally molded brush. The integrally molded brush comprises: a) a generally planar hub having an outer periphery, where the hub has a thickness of at least 0.05 inches; and b) a plurality of bristles extending from the outer periphery of the hub, where each of the bristles includes a bristle tip opposite the hub, where the bristle tip has a thickness up to 0.03 inches, where the molded brush comprises a thermoplastic polymeric material.
In one preferred embodiment of the above molded brush, the plurality of bristles are arranged in at least two rows extending from the outer periphery of the hub. In another aspect of this embodiment, the plurality of bristles are arranged in at least three rows extending from the outer periphery of the hub.
In another preferred embodiment of the above molded brush, the hub has a thickness of at least 0.06 inches, and where the bristle tip has a thickness up to 0.02 inches. In another preferred embodiment of the above molded brush, the hub has a thickness of 0.05 inches to 0.09 inches, and where the bristle tip has a thickness of 0.015 inches to 0.03 inches. In yet another preferred embodiment of the above molded brush, the outer periphery of the hub includes a diameter of 1.5 inches to 6.0 inches. In another preferred embodiment of the above molded brush, the hub further includes an inner periphery opposite the outer periphery, and where the inner periphery includes a diameter of 0.5 inches to 4 inches.
In another preferred embodiment of the above molded brush, each of the bristles includes a bristle length, and where the bristle length of 0.25 inches to 2.5 inches. In another preferred embodiment of the above molded brush, the brush includes a diameter of 6 inches to 8 inches. In yet another preferred embodiment of the above molded brush, each of the bristles includes a taper so as to be thicker adjacent the hub than at the bristle tip. In another preferred embodiment of the above molded brush, each of the bristles includes a bristle root adjacent the outer periphery of the center portion, where the bristle root includes a bristle thickness of 0.02 inches to 0.108 inches.
In yet another preferred embodiment of the above molded brush, the molded brush comprises a thermoplastic elastomer. In another preferred embodiment of the above molded brush, the molded brush includes abrasive particles interspersed in the thermoplastic polymeric material.
Another aspect of the present invention provides an alternative integrally molded brush. The integrally molded brush comprises: a) a generally planar hub having an outer periphery and an inner periphery opposite the outer periphery, where the hub has a thickness of 0.05 inches to 0.09 inches, where the outer periphery of the hub includes a diameter of 1.5 inches to 6 inches, where the inner periphery includes a diameter of 0.5 inches to 4 inches; and b) a plurality of bristles extending from the outer periphery of the hub, where each of the bristles includes a bristle tip opposite the hub, where the bristle tip has a thickness of 0.015 inches to 0.03 inches, where each of the bristles includes a bristle length, where the bristle length is in the range of 0.25 inches to 2.5 inches, and where each of the bristles includes a taper so as to be thicker adjacent the hub than at the bristle tip, where the molded brush comprises a thermoplastic elastomer, and where the molded brush includes abrasive particles in throughout the thermoplastic elastomer.
Another aspect of the present invention provides a method of molding an integrally molded brush. The method of molding an integrally molded brush, comprises the steps of: a) heating a thermoplastic polymer to sufficiently high temperature to allow the thermoplastic polymer to be injected into a mold; b) injecting the thermoplastic polymer under pressure into a mold, where the mold includes a hub section and a plurality of bristle sections in fluid communication with the hub section, where the hub section includes a thickness of at least 0.05 inches, where each of the bristle sections includes a bristle tip section opposite the hub section, and where the bristle tip section has a thickness up to 0.03 inches; c) injecting the thermoplastic polymer under pressure into the hub section of the mold, while maintaining the thermoplastic polymer at a high enough temperature to prevent solidification of the thermoplastic polymer; d) injecting the thermoplastic polymer under pressure into the plurality of bristle sections of the mold so as to substantially fill the plurality of bristle sections with the thermoplastic polymer; e) sufficiently cooling the thermoplastic polymer to allow the integrally molded brush to be removed from the mold; f) thereafter removing the integrally molded brush from the mold.
In another preferred embodiment of the above method, the mold includes a plurality of gates, and where the gates are in fluid communication with the hub section of the mold, and where the plurality of bristle sections extend from the hub section of the mold opposite the plurality of gates. In yet another preferred embodiment of the above method, the thermoplastic polymer includes abrasive particles therein.